U.S. patent application number 16/541297 was filed with the patent office on 2020-02-27 for manufacturing hydrocarbons.
The applicant listed for this patent is ExxonMobil Research and Engineering Company. Invention is credited to Guang Cao, Suzzy C. Ho, Matthew S. Ide, Brian M. Weiss, Sara L. Yohe.
Application Number | 20200063043 16/541297 |
Document ID | / |
Family ID | 69584400 |
Filed Date | 2020-02-27 |
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United States Patent
Application |
20200063043 |
Kind Code |
A1 |
Ide; Matthew S. ; et
al. |
February 27, 2020 |
MANUFACTURING HYDROCARBONS
Abstract
A system and methods for manufacturing a base oil stock from a
light hydrocarbon stream are provided. An example method includes
cracking a light hydrocarbon stream to form an impure olefinic
stream, separating water from the impure olefinic stream, and
oligomerizing the impure olefinic stream to form a raw oligomer
stream. A light olefinic stream from the raw oligomer stream and
linear alpha olefins are recovered from the light olefinic stream.
A heavy olefinic stream is distilled from the raw oligomer stream
and hydro-processed to form a hydro-processed stream. They
hydro-processed stream is distilled to form the base oil stock.
Inventors: |
Ide; Matthew S.;
(Doylestown, PA) ; Ho; Suzzy C.; (Princeton,
NJ) ; Cao; Guang; (Princeton, NJ) ; Weiss;
Brian M.; (Bridgewater, NJ) ; Yohe; Sara L.;
(Houston, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ExxonMobil Research and Engineering Company |
Annandale |
NJ |
US |
|
|
Family ID: |
69584400 |
Appl. No.: |
16/541297 |
Filed: |
August 15, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62721157 |
Aug 22, 2018 |
|
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|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 2531/842 20130101;
B01J 31/183 20130101; C10G 67/02 20130101; C10G 2400/10 20130101;
B01J 31/1815 20130101; B01J 2231/20 20130101; C10G 50/02 20130101;
C10G 2400/20 20130101; C10G 47/02 20130101; C10G 2400/22
20130101 |
International
Class: |
C10G 67/02 20060101
C10G067/02; C10G 47/02 20060101 C10G047/02; C10G 50/02 20060101
C10G050/02; B01J 31/18 20060101 B01J031/18 |
Claims
1. A system for manufacturing a base oil stock from a light
hydrocarbon stream, comprising: a cracker configured to form a raw
hydrocarbon stream from the light hydrocarbon stream; a separator
configured to separate a raw olefinic stream from the raw
hydrocarbon stream; an oligomerization reactor configured to
increase a number of carbon atoms in molecules of the raw olefinic
stream forming a raw oligomer stream; a distillation column
configured to separate the raw oligomer stream into: a light
olefinic stream, wherein the light olefinic stream is provided to
another separator for the isolation of light linear alpha-olefins;
an intermediate olefinic stream; and a heavy olefinic stream; a
hydro-processing reactor configured to hydro-process the heavy
olefinic stream to form a hydro-processed stream; and a product
distillation column configured to separate the hydro-processed
stream to form the base oil stock.
2. The system of claim 1, comprising a dimerization reactor
configured to dimerize the intermediate olefinic stream and return
a dimerized stream to the distillation column.
3. The system of claim 1, comprising an alkylation reactor
configured to alkylate the intermediate olefinic stream and provide
a raw alkylated stream to an alkylation distillation column.
4. The system of claim 3, wherein the alkylation distillation
column is configured to separate an unreacted olefin stream from
the raw alkylated stream and return the unreacted olefin stream to
the alkylation reactor.
5. The system of claim 3, wherein the alkylation distillation
column is configured to separate an alkylated stream from the raw
alkylated stream and provide the alkylated stream to the
hydro-processing reactor.
6. The system of claim 1, wherein the separator comprises: a
primary fractionator configured to remove tar and steam cracker gas
oil from the raw hydrocarbon stream; a caustic tower configured to
remove hydrogen sulfide and carbon dioxide from the raw hydrocarbon
stream; and a dryer configured to remove water from the raw
hydrocarbon stream.
7. The system of claim 1, wherein the oligomerization reactor is
configured to use a homogeneous catalyst.
8. The system of claim 7, wherein the homogeneous catalyst
comprises an iron (II) pyridine-bis-imine (Fe-PBI) catalyst
comprising a structure of: ##STR00006## wherein Rn comprises one,
two, or three substituents; and wherein the substituents comprise
CH.sub.3, F, or both.
9. The system of claim 1, wherein the hydro-processing reactor
comprises a demetallation unit.
10. The system of claim 1, wherein the hydro-processing reactor
comprises a hydrocracking unit.
11. The system of claim 1, wherein the hydro-processing reactor
comprises a hydroisomerization unit.
12. The system of claim 1, wherein the distillation column is
configured to separate the hydro-processed stream into: a
distillate stream comprising naphtha; a heavy neutral stream; a
medium neutral stream; and a light neutral stream.
13. A method for manufacturing a base oil stock from a light
hydrocarbon stream, comprising: cracking the light hydrocarbon
stream to form an impure olefinic stream; separating water from the
impure olefinic stream; oligomerizing the impure olefinic stream to
form a raw oligomer stream; distilling a light olefinic stream from
the raw oligomer stream and recovering alpha olefins from the light
olefinic stream; distilling a heavy olefinic stream from the raw
oligomer stream; hydro-processing the heavy olefinic stream to form
a hydro-processed stream; and distilling the hydro-processed stream
to form the base oil stock.
14. The method of claim 13, comprising distilling an intermediate
olefinic stream from the raw oligomer stream.
15. The method of claim 14, comprising: dimerizing the intermediate
olefinic stream to form a dimerized stream; and distilling the
dimerized stream with the raw oligomer stream.
16. The method of claim 14, comprising: alkylating the intermediate
olefinic stream to form an alkylated stream; distilling the
alkylated stream to form a lights stream and a heavies stream;
combining the lights stream with the intermediate olefinic stream
to form a combined stream; and alkylating the combined stream.
17. The method of claim 16, comprising hydro-processing the heavies
stream.
18. The method of claim 13, wherein oligomerizing the impure
olefinic stream comprises contacting the impure olefinic stream
with a homogeneous catalyst comprising an iron (II)
pyridine-bis-imine.
19. The method of claim 13, comprising: separating an unreacted
ethylene stream from the raw oligomer stream; and oligomerizing the
unreacted ethylene stream with the impure olefinic stream.
20. The method of claim 13, wherein hydro-processing the heavy
olefinic stream comprises hydrocracking the heavy olefinic
stream.
21. The method of claim 13, wherein hydro-processing the heavy
olefinic stream comprises hydroisomerizing the heavy olefinic
stream.
22. The method of claim 13, wherein distilling the hydro-processed
stream comprises separating a distillate stream, a naphtha stream,
or both from the hydro-processed stream.
23. The method of claim 13, wherein distilling the hydro-processed
stream comprises forming a heavy neutral oil stock stream, a medium
neutral oil stock stream, or a light neutral oil stock stream, or
any combinations thereof.
24. A system for manufacturing a base oil stock from a light
hydrocarbon stream, comprising: a steam cracker to form an impure
olefinic stream from the light hydrocarbon stream; a separator
configured to remove naphtha, water, steam cracker gas oil (SCGO),
and tar from the impure olefinic stream; an oligomerization reactor
configured to convert the impure olefinic stream to a higher
molecular weight stream by contacting the impure olefinic stream
with a homogeneous catalyst; a distillation column configured to
recover a light olefinic stream; the distillation column configured
to separate an intermediate olefinic stream from the higher
molecular weight stream and send the intermediate olefinic stream
to a dimerization reactor or an alkylation reactor; the
distillation column configured to separate a heavy olefinic stream
from the higher molecular weight stream; a hydro-processing reactor
configured to demetallate the heavy olefinic stream, to crack the
heavy olefinic stream, to form isomers in the heavy olefinic
stream, or to hydrogenate olefinic bonds in the heavy olefinic
stream, or any combinations thereof; and a product distillation
column to separate the isomers in the heavy olefinic stream to form
a plurality of base oil stock streams.
25. The system of claim 24, wherein the dimerization reactor is
configured to dimerize the intermediate olefinic stream to form a
dimerized stream and return the dimerized stream to the
distillation column.
26. The system of claim 24, wherein the alkylation reactor is
configured to alkylate the intermediate olefinic stream to form an
alkylated stream.
27. The system of claim 26, comprising an alkylation distillation
column configured to separate the alkylated stream into a reacted
stream and an unreacted stream, and return the unreacted stream to
the alkylation reactor.
28. The system of claim 24, wherein the homogeneous catalyst
comprises an iron (II) pyridine-bis-imine (Fe-PBI) compound
comprising a structure of: ##STR00007## wherein Rn comprises one,
two, or three substituents; and wherein the substituents comprise
CH.sub.3, F, or both.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional
Application No. 62/721,157, filed on Aug. 22, 2019, the entire
contents of which are incorporated herein by reference.
FIELD
[0002] The techniques described herein provide systems and methods
for manufacturing a lubricant base stock from a light hydrocarbon
stream. The light hydrocarbon stream is processed in to generate a
mixture of compounds that are oligomerized and hydro-processed to
form the base oil stock.
BACKGROUND
[0003] This section is intended to introduce various aspects of the
art, which may be associated with exemplary examples of the present
techniques. This description is believed to assist in providing a
framework to facilitate a better understanding of particular
aspects of the present techniques. Accordingly, it should be
understood that this section should be read in this light, and not
necessarily as admissions of prior art.
[0004] High molecular weight paraffins suitable for the production
of high quality hydrocarbon fluids, such as base oil stocks and
distillate fuel, are typically in short supply or expensive to
manufacture. In addition, the oligomerization of olefins is
typically performed with high purity feed streams, such as polymer
grade ethylene.
[0005] The production of higher molecular weight linear paraffins
and isoparaffins, for example, to form base oil stocks, from
hydrocarbon streams may involve numerous steps, which affect the
costs for the final products. One example of the production of
these compounds is the production of syngas, CO and H.sub.2 by
steam reforming of methane, followed by methanol synthesis. The
methanol may then be converted to olefins via a methane-to-olefins
(MTO) process. The olefins are further oligomerized to higher
molecular weight hydrocarbons. In another example, syngas is
produced for use in Fischer-Tropsch reactions which preferentially
synthesize linear high molecular weight products. However, these
options may be economically problematic due to the need to first
produce syngas.
[0006] Some previous research activities have focused on using
impure ethylene feeds to produce polyalphaolefins (PAOs). For
example, U.S. Patent Application Publication No. 2010/0249474 by
Nicholas et al. discloses a "process for oligomerizing dilute
ethylene." As described in the publication, a fluid catalytic
cracking process (FCC) may provide a dilute ethylene stream, as
heavier hydrocarbons are processed. The ethylene in the dilute
ethylene stream may be oligomerized using a catalyst, such as an
amorphous silica-alumina base with a Group VIII or VIB metal that
is resistant to feed impurities such as hydrogen sulfide, carbon
oxides, hydrogen and ammonia. About 40 wt. %, or greater, of the
ethylene in the dilute ethylene stream can be converted to heavier
hydrocarbons.
[0007] Further, U.S. Patent Application Publication No.
2014/0275669 by Daage et al., discloses the "production of
lubricant base oils from dilute ethylene feeds." As described in
this publication, a dilute ethylene feed, for example, formed while
cracking heavier hydrocarbons, may be oligomerized to form
oligomers for use as fuels or lubricant base oils. The
oligomerization of the impure dilute ethylene is performed with a
zeolitic catalyst. The zeolitic catalyst is resistant to the
presence of poisons such as sulfur and nitrogen in the ethylene
feed. Diluents such as light paraffins, may be present without
interfering with the process.
[0008] The feed used for both processes described above is derived
from the processing of oil in a fluid catalytic cracker (FCC). In
an FCC, heavier hydrocarbons, such as crude oil fractions with a
molecular weight of about 200 to about 600, or higher, are
contacted with a catalyst at high temperatures to form lower
molecular weight compounds. The byproduct gases from the FCC
include olefins that may be used to form the oligomers.
[0009] The oligomerization of blends of ethylene with co-monomers,
such as 1-hexene, 1-heptene, 1-octene, 1-dodecene, and
1-hexadecene, has been explored. For example, U.S. Pat. No.
7,238,764 describes a process for the co-oligomerization of
ethylene and alpha olefins. The co-oligomerization of the alpha
olefins with ethylene is performed in the presence of a metal
catalyst system. The metal catalyst system may include
bis-aryliminepyridine MX.sub.a complexes, [bis-aryliminepyridine
MY.sub.p.Lb.sup.+] [NC.sup.-].sub.q complexes, or both. The process
is carried out in an ethylene pressure of less than about 2.5
megapascals (MPa).
SUMMARY
[0010] In an embodiment, the present invention provides a system
for manufacturing a base oil stock from a light hydrocarbon stream.
The system includes a cracker configured to form a raw hydrocarbon
stream from the light hydrocarbon stream, a separator configured to
separate a raw olefinic stream from the raw hydrocarbon stream, and
an oligomerization reactor configured to increase a number of
carbon atoms in molecules of the raw olefinic stream forming a raw
oligomer stream. A distillation column is configured to separate a
light olefinic stream from the raw oligomer stream for recovery of
light linear alpha olefins. The distillation column is configured
to further separate the raw oligomer stream into an intermediate
olefinic stream and a heavy olefinic stream. A hydro-processing
reactor is configured to hydro-process the heavy olefinic stream to
form a hydro-processed stream. A product distillation column is
configured to separate the hydro-processed stream to form the base
oil stock.
[0011] In another embodiment, the present invention provides a
method for manufacturing a base oil stock from a light hydrocarbon
stream. The method includes cracking a light hydrocarbon stream to
form an impure olefinic stream, separating water from the impure
olefinic stream, and oligomerizing the impure olefinic stream to
form a raw oligomer stream. A light olefinic stream is distilled
from the raw oligomer stream and linear alpha olefins are recovered
from the light olefinic stream. A heavy olefinic stream is
distilled from the raw oligomer stream and hydro-processed to form
a hydro-processed stream. The hydro-processed stream is distilled
to form the base oil stock.
[0012] In another embodiment, the present invention provides a
system for manufacturing a base oil stock from a light hydrocarbon
stream. The system includes a steam cracker to form an impure
olefinic stream from the light hydrocarbon stream, and a separator
configured to remove naphtha, water, steam cracker gas oil (SCGO),
and tar from the impure olefinic stream. An oligomerization reactor
is configured to convert the impure olefinic stream to a higher
molecular weight stream by contacting the impure olefinic stream
with a homogeneous catalyst. A distillation column is configured to
recover a light olefinic stream and provide the light olefinic
stream to a recovery system for the recovery of light alpha
olefins. The distillation column is configured to separate an
intermediate olefinic stream from the higher molecular weight
stream and send the intermediate olefinic stream to a dimerization
reactor or an alkylation reactor. The distillation column is
configured to separate a heavy olefinic stream from the higher
molecular weight stream. A hydro-processing reactor is configured
to demetallate the heavy olefinic stream, to crack the heavy
olefinic stream, to form isomers in the heavy olefinic stream, or
to hydrogenate olefinic bonds in the heavy olefinic stream, or any
combinations thereof. A product distillation column is configured
to separate the isomers in the heavy olefinic stream to form a
plurality of base oil stock streams.
DESCRIPTION OF THE DRAWINGS
[0013] The advantages of the present techniques are better
understood by referring to the following detailed description and
the attached drawings.
[0014] FIG. 1(A) is a simplified block diagram of a system for
producing base oil stocks from a light feedstock, in accordance
with examples.
[0015] FIG. 1(B) is a simplified block diagram of a system for
removing water from an impure ethylene stream formed from a light
feedstock, in accordance with examples.
[0016] FIG. 2 is a simplified block diagram of another system for
producing base oil stocks from a light feedstock, in accordance
with examples.
[0017] FIG. 3 is a process flow diagram of a method for producing
base oil stocks from a light feedstock, in accordance with
examples.
[0018] FIG. 4 is a plot showing the selective hydrogenation of
carbon monoxide, in accordance with examples.
[0019] FIGS. 5(A)-5(F) are drawings of different homogeneous
catalysts that can be used for oligomerization, in accordance with
examples.
[0020] FIG. 6 is a plot of the Schultz-Flory distribution of a
product that includes different carbon numbers, in accordance with
examples.
[0021] FIG. 7 is a plot of the effect of the change in carbon
number composition on a weight fraction of a product as the
Schultz-Flory distribution changes, in accordance with
examples.
[0022] FIG. 8 is a plot of an IR spectrum showing the incorporation
of acetylene into the product, in accordance with examples.
[0023] FIG. 9 is an infrared micrograph, showing the presence of
polyacetylene in a product, in accordance with examples.
[0024] FIG. 10 is a plot comparing ligand structure to the yield of
higher carbon number compounds, in accordance with examples.
[0025] FIGS. 11(A)-11(C) are three plots showing the ability to
tune the molecular weight distribution of the products using ligand
modification, in accordance with examples.
DETAILED DESCRIPTION
[0026] In the following detailed description section, specific
embodiments of the present techniques are described. However, to
the extent that the following description is specific to a
particular embodiment or a particular use of the present
techniques, this is intended to be for exemplary purposes only and
simply provides a description of the exemplary embodiments.
Accordingly, the techniques are not limited to the specific
embodiments described below, but rather, include all alternatives,
modifications, and equivalents falling within the true spirit and
scope of the appended claims.
[0027] Recent improvements in the production of hydrocarbons, for
example, the use of hydraulic fracturing and tertiary oil recovery
techniques, have resulted in the increased availability of lower
molecular weight hydrocarbons, termed light hydrocarbon streams
herein. These include natural gas and natural gas liquids (NGL),
which may include methane, ethane, propane, and butane, along with
other hydrocarbon and heteroatom contaminants. The use of the lower
molecular weight hydrocarbons as feedstocks for chemical processes
may provide economic benefits. However, upgrading the lower
molecular weight feedstocks to increase the molecular weight may
pose challenges.
[0028] The techniques described herein disclose a method for
producing high molecular weight molecules from a raw olefin stream
that may include olefins, paraffins, hydrogen, and carbon monoxide.
The raw olefin stream is provided by a steam cracking reactor, or
cracker, which may be controlled to provide a higher molecular
weight feed stock from a light hydrocarbon stream. The light
hydrocarbon stream has an API gravity of at least 45, at least 50,
at least 55, at least 60, at least 65, or at least 70 according to
various embodiments of the present invention. Further, the hydrogen
content of the starting raw hydrocarbons may be greater than or
equal to 14%, or, in some examples, greater or equal to 16%. In
some examples, the light hydrocarbon stream may also include
compounds having two to four, two to six, two to 12, or two to 20
carbon atoms. In some examples, the feed is a natural gas liquids
(NGL) stream. In other examples, the feed includes methane, ethane,
propane, or butane. In some examples, the light hydrocarbon
feedstock has an API gravity of between about 45 and 55 and
includes molecules with carbon chains of about two to 25 carbon
atoms in length, among others. In other examples, the light
hydrocarbon feedstock has an API gravity of between about 55 and 65
and includes molecules with about two to 10 carbon atoms, among
others. In other examples, the light hydrocarbon feedstock has an
API gravity of between about 55 and 65 and includes molecules with
about two to 10 carbon atoms, among others. In yet other examples,
the light hydrocarbon feedstock has an API gravity of between about
65 and 75 and includes molecules with about two to five carbon
atoms, among others.
[0029] The light hydrocarbon stream may be sourced from any number
of hydrocarbon formations, including, for example, tight gas
formations. These may include the Clinton, Medina, and Tuscarora
formations in Appalachia, the Berea sandstone in Michigan, the
Bossier, Cotton Valley, Olmos, Vicksburg, and Wilcox Lobo
formations along the Gulf Coast, the Granite Wash and Atoka
formations in the Midcontinent, the Canyon formation and other
formations, in the Permian Basin, and the Mesaverde and Niobrara
formations in multiple Rocky Mountain basins. Any number of other
formations may be used to provide the light hydrocarbon stream,
such as the Rotliegend Group of formations in Germany and the
Netherlands, the Eagle Ford group in Texas, and the Bakken
formations in Montana, North Dakota, Saskatchewan, and
Manitoba.
[0030] As used herein, "base stock" or "base oil stock" refers to
semi-synthetic or synthetic isoparaffins that may be used in the
production of compounds in a lubricant range of molecular weights.
Group I base oil stocks or base oils are defined as base oils with
less than 90 wt. % saturated molecules and/or at least 0.03 wt. %
sulfur content. Group I base oil stocks also have a viscosity index
(VI) of at least 80 but less than 120. Group II base oil stocks or
base oils contain at least 90 wt. % saturated molecules and less
than 0.03 wt. % sulfur. Group II base oil stocks also have a
viscosity index of at least 80 but less than 120. Group III base
oil stocks or base oils contain at least 90 wt. % saturated
molecules and less than 0.03 wt. % sulfur, with a viscosity index
of at least 120. Other hydrocarbons that may be coproduced with
base oil stocks include gasoline, diesel fuels, distillates, and
other hydrocarbon fluids.
[0031] Further, the base oil stocks may be referred to as light
neutral (LN), medium neutral (MN), and heavy neutral (HN), for
example, as determined by viscosity. The term "neutral" generally
indicates the removal of most nitrogen and sulfur atoms to lower
reactivity in the final oil. The base oil stocks are generally
classified by viscosity, measured at 100.degree. C. as a kinematic
viscosity under the techniques described in ASTM D445. The
viscosity may be reported in millimeters{circumflex over (
)}2/second (centistokes, cSt). The base oil stocks may also be
classified by boiling point range, for example, determined by
simulated distillation on a gas chromatograph, under the techniques
described in ASTM D 2887.
[0032] It may be noted that the viscosity ranges and boiling point
ranges described herein are merely examples, and may change,
depending on the content of linear paraffins, branched paraffins,
cyclic hydrocarbons, and the like. A light neutral base oil stock
may have a kinematic viscosity of about 4 cSt to about 6 cSt and
may have a boiling point range of about 380.degree. C. to about
450.degree. C. A medium neutral base oil stock may have a kinematic
viscosity of about 6 cSt to about 10 cSt and a boiling point range
of about 440.degree. C. to about 480.degree. C. A heavy neutral
base oil stock may have a kinematic viscosity of about 10 cSt to
about 20 cSt, or higher, and a boiling point range of about
450.degree. C. to about 565.degree. C.
[0033] As used herein "cracking" is a process that uses
decomposition and molecular recombination of organic compounds to
produce a greater number of molecules than were initially present.
In cracking, a series of reactions take place accompanied by a
transfer of hydrogen atoms between molecules. Cracking may be
performed in a thermal cracking process, a steam cracking process,
a catalytic cracking process, or a hydrocracking process, among
others. For example, naphtha, a hydrocarbon mixture that is
generally a liquid having molecules with about five to about twelve
carbon atoms, may undergo a thermal cracking reaction to form
ethylene and H.sub.2 among other molecules. In some examples, the
free radicals formed during the cracking process may form compounds
that are more complex than those in the feed.
[0034] As used herein, a "catalyst" is a material that increases
the rate of specific chemical reactions under certain conditions of
temperature and pressure. Catalysts may be heterogeneous,
homogenous, and bound. A heterogeneous catalyst is a catalyst that
has a different phase from the reactants. The phase difference may
be in the form of a solid catalyst with liquid or gaseous reactants
or in the form of immiscible phases, such as an aqueous acidic
catalyst suspended in droplets in an organic phase holding the
reactants. A heterogeneous catalyst may be bound, such as a zeolite
bound with alumina or another metal oxide. A homogeneous catalyst
is soluble in the same phase as the reactants, such as an
organometallic catalyst dissolved in an organic solvent with a
reactant.
[0035] The processed impure feed stream is then introduced to a
reaction zone in an oligomerization reactor where a homogeneous
catalyst, for example, as described with respect to FIG. 5, is used
to generate oligomers in an oligomerization process. The
oligomerization reaction forms oligomers by reacting small molecule
olefins, such as ethylene and propylene, termed monomers, to form a
short chain or oligomer. The oligomers may include two to 50
monomers, or more, depending on the reaction conditions used. The
oligomers may be linear alpha-olefins with a Schulz-Flory (S-F)
distribution. As used herein, an S-F distribution is a probability
distribution that describes the relative ratios of oligomers of
different lengths that occur in an ideal step-growth
oligomerization process. Generally, shorter oligomers are favored
over longer oligomers.
[0036] However, the S-F distribution of the olefinic products may
be controlled by the selection of an organic ligand on the
catalyst, or through the selection of reaction conditions such as
temperature and pressure. These choices may be used to enhance the
production of either light LAOs or heavier, base stock range
molecules. The product olefins may then be split into light
olefinic (C12-), medium olefinic (C12-C22), and heavy olefinic
(C24+) fractions, for example, through conventional distillation.
It may be noted that the olefinic fractions may not be pure
olefins, but may include other compounds with similar boiling
points, such as paraffinic compounds. The light fraction may
include C4, C6, C8, C10, and C12 LAOS, the medium fraction may be
sent to a dimerization or alkylation reactor using a catalyst
selected from a variety of heterogeneous or homogeneous catalysts,
and the heavy fraction may be sent to a demetallation zone or stage
then to a hydrocracking/hydroisomerization (HDC/HDI) reactor to
produce the high quality (Group III) base stock.
[0037] The ability to control the S-F distribution makes the
targeted production of particular products possible. In some
examples, an S-F distribution of about 0.75 to about 0.91 is
targeted to make various wax and base stock products with carbon
numbers of at least 24. In other examples, an S-F distribution of
about 0.83 to about 0.87 is targeted to make products having about
24 to about 50 carbon atoms, such as lower viscosity base stocks.
In further examples, an S-F distribution of about 0.6 to about 0.75
is targeted to make products having about four to about 22 carbon
atoms, such as various linear alpha olefins. The relation of S-F
distribution to various carbon numbers is discussed with respect to
FIG. 7.
[0038] The oligomerization of low molecular weight olefins, such as
ethylene, usually requires a complex and expensive purification
scheme to recover high purity ethylene from light hydrocarbon
streams created as byproducts in cracking processes. The cost of
olefin purification can be from one half to two thirds of the cost
of producing high purity ethylene. This provides a number of
advantages over previous techniques, including the use of low cost
hydrocarbon feedstocks, such as a light hydrocarbon feed from
hydraulic fracturing, to produce high value base oil stock. The
techniques may also use hydro-processing to perform demetallation
during the production of alpha-olefins, when using a metal
containing homogeneous catalyst, which may lower the cost over an
aqueous quench and extraction process that uses waste water
separation and treatment.
[0039] For ease of reference, certain terms used in this
application and their meanings as used herein are set forth. To the
extent a term is not defined herein, it should be given the
broadest definition persons in the pertinent art have given that
term as reflected in at least one printed publication or issued
patent. Further, the present techniques are not limited by the
usage of the terms shown herein, as all equivalents, synonyms, new
developments, and terms or techniques that serve the same or a
similar purpose are considered to be within the scope of the
present claims.
[0040] In an example of a process to convert light hydrocarbons to
lubricant base oil stock, for example, using the system and method
described in greater detail with respect to FIGS. 1(A) and 2, a
light gas stream, that may include ethane, is converted, via steam
cracking, to an impure olefinic stream or raw product stream. The
raw product stream is then sent to a quench fractionator where
naphtha, water, steam cracking gas oil, and tar are separated out
to form an oligomerization feed stream. The oligomerization feed
stream may contain ethylene, propylene, acetylene, propyne,
hydrogen, carbon monoxide, methane, ethane, propane, hydrogen
disulfide, carbon monoxide, and water. Additional impurities in the
ppb level such as Hg, PH.sub.3, AsH.sub.3, COS, and NO.sub.x may
also be contained in the stream.
[0041] The oligomerization feed stream may be processed by a
caustic tower to remove H.sub.2S and CO.sub.2 as well as a drier to
remove excess water. As used herein, a "caustic tower" is a
separation tower in which a caustic solution, such as an aqueous
solution of sodium hydroxide, is contacted with a hydrocarbon
stream to remove some heteroatom impurities, such as sulfur
compounds and carbon dioxide. The caustic tower may use any number
of internal flow arrangements, such as co-current flows and
counter-current flows, among others. Other units, such as settlers,
may be used with the caustic tower to separate the hydrocarbon from
the caustic solution.
[0042] The impure olefinic stream is provided to the
oligomerization reactor, which converts the olefins to higher
molecular weight products. The conversion could be performed in a
number of different reactor types including but not limited to a
fixed bed, a slurry-bubble column, a CSTR, or a moving bed.
Generally, the catalyst is a homogeneous catalyst, as described
with respect to FIGS. 5(A) to 5(E).
[0043] The higher molecular weight products containing gasoline,
diesel, and base oil stock can either be used as is or can then be
hydrotreated to remove heteroatoms and saturate olefins. The
process conditions and catalyst for the hydro-processing of
paraffins and isoparaffins may be as described above.
[0044] A separation train after a steam cracking reactor may
include over a dozen steps and pieces of equipment to produce high
purity polymer grade ethylene. In addition, the raw product stream
may be compressed from about 10 psig to about 550 psig before
entering a cold box to remove H.sub.2, CO, and CH.sub.4 impurities.
Decreasing the process pressure greatly reduces the cost of
separation and thus the overall process. An exemplary simple
separation may include a primary fractionator, a caustic tower, a
drier, and an acetylene converter. Further, the raw product stream
may be compressed to only about 250 psig to implement the simple
separation, lowering costs over compression to 550 psig. The
elimination of the remaining back-end separation train decreases
the cost of production, but produces an impure olefin stream that
can be processed by the impure olefin stream conversion process to
produce higher molecular weight products.
[0045] FIG. 1(A) is a simplified block diagram of a system 100 for
producing high quality hydrocarbons from a light hydrocarbon feed,
in accordance with examples. The process begins with the
introduction of a hydrocarbon feed stream, such as a light
hydrocarbon stream 102, to a steam cracking reactor 104, or
cracker. As used herein, a hydrocarbon feed stream may include a
composition prior to any treatment, such treatment including
cleaning, dehydration or scrubbing, as well as any composition
having been partly, substantially or wholly treated for the
reduction or removal of one or more compounds or substances,
including, but not limited to, sulphur, sulphur compounds, carbon
dioxide, water, mercury.
Steam Cracking
[0046] In the steam cracking reactor 104, the light hydrocarbon
stream 102 is diluted with steam, and then briefly heated to high
temperatures in a steam cracker, such as above 800.degree. C.,
before the reaction is quenched. The reaction time may be
milliseconds in length. Oxygen is excluded to prevent degradation
and decrease the formation of carbon oxides. The mixture of
products in the raw product stream 106 from the steam cracking
reactor 104 may be controlled by the feedstock, with the lighter
feedstocks of the light hydrocarbon stream 102, such as ethane,
propane, or butane, or combinations thereof, among others, favoring
the formation of lighter products, such as ethylene, propylene, or
butadiene, among others. The product distribution in the raw
product stream 106 may also be controlled by the steam/hydrocarbon
ratio, the reaction temperature, and the reaction time, among other
factors.
[0047] A separator 108 may be used to separate the water formed
from the steam and degradation products of the raw product stream
106 to form an oligomerization feed stream 110. The separator 108
may include a flash tank to allow water to condense and settle,
while product gases flow out, forming the oligomerization feed
stream 110. In another example, the separator may be a condenser,
as described with respect to FIG. 1(B).
[0048] After water removal, the oligomerization feed stream 110 may
include, for example, approximately 5% to 90% olefin (ethylene,
propylene, butylene, and the like), 5% to 80% hydrogen, 0 to 20%
alkyne (acetylene, propyne, and the like), 0% to 50% paraffin
(methane, ethane, C3+), 10 to 10,000 wt. ppm of carbon monoxide,
and trace water. In some examples, the oligomerization feed stream
110 includes 35% to 55% olefin, 30% to 60% hydrogen, 0.5% to 3%
alkyne, 5% to 30% paraffin, and 500 to 2,000 wt. ppm of carbon
monoxide.
Oligomerization
[0049] The oligomerization feed stream 110 is provided to an
oligomerization reactor 112, where it may be contacted with a
homogeneous catalyst 114, for example, an organometallic catalyst.
In examples described herein, the homogeneous catalyst 114 is
generally an impurity tolerant homogeneous catalyst, such as an
Iron (II) pyridine-bis-imide (Fe-PBI), capable of the
oligomerization of the oligomerization feed stream 110 to C10+
products, C25+, or C50+ products, to produce diesel, lube, and
heavier hydrocarbon molecules, such as the base oil stocks.
[0050] An example of a homogenous catalyst that may used includes
an iron (II) pyridine-bis-imine (Fe-PBI) compound having a
structure of formula 1:
##STR00001##
In formula 1, X is a halogen or hydrocarbyl radical, such as C1.
Each R substituent is independently a halogen or hydrocarbyl
radical, and each n is an integer from 1-5 representing the number
of R groups present. Each n is 1, 2 or 3. In some examples, n is 2
or 3. Each R is a C1-C10 alkyl, or a halogen. In some examples, R
is methyl, ethyl or n-propyl. In some examples, at least one R is
methyl. In some examples, at least one R is fluorine. In some
examples, Rn comprises one, two, or three substituents, wherein
each of the substituents is methyl, or fluorine. Each R.sup.a, and
R.sup.b are independently a hydrogen, halogen or hydrocarbyl
radical. In some examples, each R.sup.a is a hydrocarbyl or
hydrogen, or a hydrogen. Each R.sup.b is a hydrocarbyl, such as a
C1-C10 alkyl, or methyl.
[0051] The homogenous catalyst may include an iron (II)
pyridine-bis-imine (Fe-PBI) compound having a structure of formula
2:
##STR00002##
In formula 2, each R.sup.a, R.sup.b and X are as defined above, and
each A is independently a substituted aryl group including one, two
or three R substituents as defined above.
[0052] In some examples, each A is defined by a structure shown in
formula 3:
##STR00003##
In formula 3, the one position of the phenyl ring is bonded to the
nitrogen of the iron (II) pyridine-bis-imine complex, and each
R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are independently
C1 to C10 alkyl, halogen or hydrogen radical. In some examples,
each R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6 are
independently methyl, ethyl, n-propyl, fluoro, and hydrogen. In
some examples, each R.sup.2, R.sup.3, R.sup.4, R.sup.5, and R.sup.6
are independently methyl, fluoro and hydrogen. In some examples,
each R.sup.2 is methyl and each R.sup.6 is fluoro. In some
examples, each R.sup.2 is fluoro and each R.sup.4 is methyl. In
some examples, each R.sup.2 and R.sup.6 are methyl, and each
R.sup.4 is fluoro. In some examples, each R.sup.2 is methyl and
each R.sup.4 is fluoro. In some examples, each R.sup.2 is methyl.
Examples of homogenous catalysts that may be used for the
oligomerization are discussed further with respect to FIGS.
5(A)-5(F). In some examples, the organometallic catalysts may be
supported to form heterogeneous catalysts.
[0053] Generally, the homogeneous catalysts are activated. After
the complexes have been synthesized, catalyst systems may be formed
by combining them with activators in any manner known from the
literature, including by supporting them for use in slurry or gas
phase polymerization reactions. The catalyst systems may also be
added to or generated in solution polymerization or bulk
polymerization (in the monomer). The catalyst system typically
includes a complex as described above and an activator such as
alumoxane or a non-coordinating anion. Activation may be performed
using alumoxane solution including methyl alumoxane, referred to as
MAO, as well as modified MAO, referred to herein as MMAO,
containing some higher alkyl groups to improve the solubility.
Particularly useful MAO can be purchased from Albemarle, typically
in a 10 wt. % solution in toluene. In some example, the catalyst
system uses an activator selected from alumoxanes, such as methyl
alumoxane, modified methyl alumoxane, ethyl alumoxane, iso-butyl
alumoxane, and the like.
[0054] When an alumoxane or modified alumoxane is used, the
complex-to-activator molar ratio is from about 1:3000 to 10:1; or
from 1:2000 to 10:1; or from 1:1000 to 10:1; or from 1:500 to 1:1;
or from 1:300 to 1:1; or from 1:200 to 1:1; or from 1:100 to 1:1;
or from 1:50 to 1:1; or from 1:10 to 1:1. When the activator is an
alumoxane (modified or unmodified), some examples select the
maximum amount of activator at a 5000-fold molar excess over the
catalyst precursor (per metal catalytic site). The preferred
minimum activator-to-complex ratio is 1:1 molar ratio.
[0055] Activation may also be performed using non-coordinating
anions, (NCAs), of the type described in European Patent
Application Nos. 277 003 A1 and 277 004 A1. An NCA may be added in
the form of an ion pair using, for example, [DMAH]+ [NCA]- in which
the N,N-dimethylanilinium (DMAH) cation reacts with a basic leaving
group on the transition metal complex to form a transition metal
complex cation and [NCA]-. The cation in the precursor may,
alternatively, be trityl. Alternatively, the transition metal
complex may be reacted with a neutral NCA precursor, such as
B(C.sub.6F.sub.5).sub.3, which abstracts an anionic group from the
complex to form an activated species. Useful activators include
N,N-dimethylanilinium tetrakis (pentafluorophenyl)borate (i.e.,
[PhNMe.sub.2H]B(C.sub.6F.sub.5).sub.4) and N,N-dimethylanilinium
tetrakis (heptafluoronaphthyl)borate, where Ph is phenyl, and Me is
methyl.
[0056] Additionally, activators useful herein include those
described in U.S. Pat. No. 7,247,687 at column 169, line 50 to
column 174, line 43, particularly column 172, line 24 to column
173, line 53. These are incorporated by reference herein.
[0057] Non-coordinating anion (NCA) is defined to mean an anion
either that does not coordinate to the catalyst metal cation or
that does coordinate to the metal cation, but only weakly. The term
NCA is also defined to include multicomponent NCA-containing
activators, such as N,N-dimethylanilinium
tetrakis(pentafluorophenyl)borate, that contain an acidic cationic
group and the non-coordinating anion.
[0058] The term NCA also includes neutral Lewis acids, such as
tris(pentafluorophenyl)boron, that can react with a catalyst to
form an activated species by abstraction of an anionic group. An
NCA coordinates weakly enough that a neutral Lewis base, such as an
olefinically or acetylenically unsaturated monomer can displace it
from the catalyst center. Any metal or metalloid that can form a
compatible, weakly coordinating complex may be used or contained in
the noncoordinating anion. Suitable metals include, but are not
limited to, aluminum, gold, and platinum. Suitable metalloids
include, but are not limited to, boron, aluminum, phosphorus, and
silicon. A stoichiometric activator can be either neutral or ionic.
The terms ionic activator, and stoichiometric ionic activator can
be used interchangeably. Likewise, the terms neutral stoichiometric
activator, and Lewis acid activator can be used interchangeably.
The term non-coordinating anion includes neutral stoichiometric
activators, ionic stoichiometric activators, ionic activators, and
Lewis acid activators.
[0059] In an example described herein, the non-coordinating anion
activator is represented by the following formula (1):
(Z).sub.d.sup.+(A.sup.d-) (1)
wherein Z is (L-H) or a reducible Lewis acid; L is a neutral Lewis
base; H is hydrogen and (L-H).sup.+ is a Bronsted acid; A.sup.d- is
a non-coordinating anion having the charge d-; and d is an integer
from 1 to 3.
[0060] When Z is (L-H) such that the cation component is (L-H)d+,
the cation component may include Bronsted acids such as protonated
Lewis bases capable of protonating a moiety, such as an alkyl or
aryl, from the catalyst precursor, resulting in a cationic
transition metal species, or the activating cation (L-H)d+ is a
Bronsted acid, capable of donating a proton to the catalyst
precursor resulting in a transition metal cation, including
ammoniums, oxoniums, phosphoniums, silyliums, and mixtures thereof,
or ammoniums of methylamine, aniline, dimethylamine, diethylamine,
N-methylaniline, diphenylamine, trimethylamine, triethylamine,
N,N-dimethylaniline, methyldiphenylamine, pyridine, p-bromo
N,N-dimethylaniline, p-nitro-N,N-dimethylaniline, phosphoniums from
triethylphosphine, triphenylphosphine, and diphenylphosphine,
oxoniums from ethers, such as dimethyl ether diethyl ether,
tetrahydrofuran, and dioxane, sulfoniums from thioethers, such as
diethyl thioethers and tetrahydrothiophene, and mixtures
thereof.
[0061] When Z is a reducible Lewis acid, it may be represented by
the formula: (Ar.sub.3C+), where Ar is aryl or aryl substituted
with a heteroatom, or a C.sub.1 to C.sub.40 hydrocarbyl, the
reducible Lewis acid may be represented by the formula:
(Ph.sub.3C+), where Ph is phenyl or phenyl substituted with a
heteroatom, and/or a C1 to C40 hydrocarbyl. In an example, the
reducible Lewis acid is triphenyl carbenium.
[0062] Examples of the anion component Ad- include those having the
formula [Mk+Qn]d- wherein k is 1, 2, or 3; n is 1, 2, 3, 4, 5 or 6,
or 3, 4, 5 or 6; n-k=d; M is an element selected from Group 13 of
the Periodic Table of the Elements, or boron or aluminum, and Q is
independently a hydride, bridged or unbridged dialkylamido, halide,
alkoxide, aryloxide, hydrocarbyl radicals, said Q having up to
about 20 carbon atoms with the proviso that in not more than one
occurrence is Q a halide, and two Q groups may form a ring
structure. Each Q may be a fluorinated hydrocarbyl radical having
about 1 to 20 carbon atoms, or each Q is a fluorinated aryl
radical, or each Q is a pentafluoryl aryl radical. Examples of
suitable Ad-components also include diboron compounds as disclosed
in U.S. Pat. No. 5,447,895, which is fully incorporated herein by
reference.
[0063] In an example in any of the NCAs represented by Formula 1
described above, the anion component Ad- is represented by the
formula [M*k*+Q*n*]d*- wherein k* is 1, 2, or 3; n* is 1, 2, 3, 4,
5, or 6 (or 1, 2, 3, or 4); n*-k*=d*; M* is boron; and Q* is
independently selected from hydride, bridged or unbridged
dialkylamido, halogen, alkoxide, aryloxide, hydrocarbyl radicals,
said Q* having up to about 20 carbon atoms with the proviso that in
not more than 1 occurrence is Q* a halogen.
[0064] The techniques describe herein also relate to a method to
oligomerize olefins including contacting olefins (such as ethylene,
butene, hexane, and others) with a catalyst complex as described
above and an NCA activator represented by the Formula (2):
R.sub.nM**(ArNHal).sub.4-n (2)
where R is a monoanionic ligand; M** is a Group 13 metal or
metalloid; ArNHal is a halogenated, nitrogen-containing aromatic
ring, polycyclic aromatic ring, or aromatic ring assembly in which
two or more rings (or fused ring systems) are joined directly to
one another or together; and n is 0, 1, 2, or 3. Typically the NCA
including an anion of Formula 2 also includes a suitable cation
that is essentially non-interfering with the ionic catalyst
complexes formed with the transition metal compounds, or the cation
is Z.sub.d.sup.+ as described above.
[0065] In an example, in any of the NCAs including an anion
represented by Formula 2 described above, R is selected from the
group consisting of C.sub.1 to C.sub.30 hydrocarbyl radicals. In an
example, C.sub.1 to C.sub.30 hydrocarbyl radicals may be
substituted with one or more C.sub.1 to C.sub.20 hydrocarbyl
radicals, halide, hydrocarbyl substituted organometalloid,
dialkylamido, alkoxy, aryloxy, alkysulfido, arylsulfido,
alkylphosphido, arylphosphide, or other anionic substituent;
fluoride; bulky alkoxides, where bulky means C.sub.4 to C.sub.20
hydrocarbyl radicals; --SRa, --NR.sup.a.sub.2, and
--PR.sup.a.sub.2, where each R.sup.a is independently a monovalent
C.sub.4 to C.sub.20 hydrocarbyl radical including a molecular
volume greater than or equal to the molecular volume of an
isopropyl substitution or a C.sub.4 to C.sub.20 hydrocarbyl
substituted organometalloid having a molecular volume greater than
or equal to the molecular volume of an isopropyl substitution.
[0066] In an example, in any of the NCAs including an anion
represented by Formula 2 described above, the NCA also includes
cation including a reducible Lewis acid represented by the formula:
(Ar.sub.3C+), where Ar is aryl or aryl substituted with a
heteroatom, and/or a C.sub.1 to C.sub.40 hydrocarbyl, or the
reducible Lewis acid represented by the formula: (Ph.sub.3C+),
where Ph is phenyl or phenyl substituted with one or more
heteroatoms, and/or C.sub.1 to C.sub.40 hydrocarbyls.
[0067] In an example in any of the NCAs including an anion
represented by Formula 2 described above, the NCA may also include
a cation represented by the formula, (L-H)d+, wherein L is an
neutral Lewis base; H is hydrogen; (L-H) is a Bronsted acid; and d
is 1, 2, or 3, or (L-H)d+ is a Bronsted acid selected from
ammoniums, oxoniums, phosphoniums, silyliums, and mixtures
thereof.
[0068] Further examples of useful activators include those
disclosed in U.S. Pat. Nos. 7,297,653 and 7,799,879, which are
fully incorporated by reference herein.
[0069] In an example, an activator useful herein includes a salt of
a cationic oxidizing agent and a non-coordinating, compatible anion
represented by the Formula (3):
(OX.sup.e+).sub.d(A.sup.d-).sub.e (3)
wherein OX.sup.e+ is a cationic oxidizing agent having a charge of
e+; e is 1, 2 or 3; d is 1, 2 or 3; and A.sup.d- is a
non-coordinating anion having the charge of d- (as further
described above). Examples of cationic oxidizing agents include:
ferrocenium, hydrocarbyl-substituted ferrocenium, Ag.sup.+, or
Pb.sup.+2. Suitable examples of A.sup.d- include
tetrakis(pentafluorophenyl)borate.
[0070] Activators useful in catalyst systems herein include:
trimethylammonium tetrakis(perfluoronaphthyl)borate,
N,N-dimethylanilinium tetrakis(perfluoronaphthyl) borate,
N,N-diethylanilinium tetrakis(perfluoronaphthyl)borate,
triphenylcarbenium tetrakis(perfluoronaphthyl)borate,
trimethylammonium tetrakis(perfluorobiphenyl)borate,
N,N-dimethylanilinium tetrakis(perfluorobiphenyl)borate,
triphenylcarbenium tetrakis(perfluorobiphenyl)borate, and the types
disclosed in U.S. Pat. No. 7,297,653, which is fully incorporated
by reference herein.
[0071] Suitable activators also include: N,N-dimethylanilinium
tetrakis (perfluoronaphthyl)borate, N,N-dimethylanilinium
tetrakis(perfluorobiphenyl)borate, N,N-dimethylanilinium
tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, triphenylcarbenium
tetrakis(perfluoronaphthyl)borate, triphenylcarbenium
tetrakis(perfluorobiphenyl)borate, triphenylcarbenium
tetrakis(3,5-bis(trifluoromethyl)phenyl)borate, triphenylcarbenium
tetrakis(perfluorophenyl)borate, [Ph3C+][B(C6F5)4-],
[Me3NH+][B(C6F5)4-];
1-(4-(tris(pentafluorophenyl)borate)-2,3,5,6-tetrafluorophenyl)pyrrolidin-
ium; and tetrakis(pentafluorophenyl)borate,
4-(tris(pentafluorophenyl)borate)-2,3,5,6-tetrafluoropyridine.
[0072] In an example, the activator includes a triaryl carbonium
(such as triphenylcarbenium tetraphenylborate, triphenylcarbenium
tetrakis(pentafluorophenyl) borate, triphenylcarbenium
tetrakis-(2,3,4,6-tetrafluorophenyl)borate, triphenyl carbenium
tetrakis(perfluoronaphthyl)borate, triphenylcarbenium
tetrakis(perfluorobiphenyl)borate, triphenylcarbenium
tetrakis(3,5-bis(trifluoromethyl) phenyl)borate).
[0073] In an example, two NCA activators may be used in the
oligomerization and the molar ratio of the first NCA activator to
the second NCA activator can be any ratio. In an example, the molar
ratio of the first NCA activator to the second NCA activator is
0.01:1 to 10,000:1, or 0.1:1 to 1000:1, or 1:1 to 100:1.
[0074] In an example, the NCA activator-to-catalyst ratio is a 1:1
molar ratio, or 0.1:1 to 100:1, or 0.5:1 to 200:1, or 1:1 to 500:1
or 1:1 to 1000:1. In an example, the NCA activator-to-catalyst
ratio is 0.5:1 to 10:1, or 1:1 to 5:1.
[0075] In an example, the catalyst compounds can be combined with
combinations of alumoxanes and NCAs (see for example, U.S. Pat.
Nos. 5,153,157; 5,453,410; European Patent Application No. EP 0 573
120 B1; WIPO Patent Publication No. WO 94/07928; and WIPO Patent
Publication No. WO 95/14044 which discuss the use of an alumoxane
in combination with an ionizing activator, all of which are
incorporated by reference herein).
[0076] In an example, when an NCA (such as an ionic or neutral
stoichiometric activator) is used, the complex-to-activator molar
ratio is typically from 1:10 to 1:1; 1:10 to 10:1; 1:10 to 2:1;
1:10 to 3:1; 1:10 to 5:1; 1:2 to 1.2:1; 1:2 to 10:1; 1:2 to 2:1;
1:2 to 3:1; 1:2 to 5:1; 1:3 to 1.2:1; 1:3 to 10:1; 1:3 to 2:1; 1:3
to 3:1; 1:3 to 5:1; 1:5 to 1:1; 1:5 to 10:1; 1:5 to 2:1; 1:5 to
3:1; 1:5 to 5:1; 1:1 to 1:1.2.
[0077] Alternately, a co-activator or chain transfer agent, such as
a group 1, 2, or 13 organometallic species (e.g., an alkyl aluminum
compound such as tri-n-octyl aluminum), may also be used in the
catalyst system herein. The complex-to-co-activator molar ratio is
from 1:100 to 100:1; 1:75 to 75:1; 1:50 to 50:1; 1:25 to 25:1; 1:15
to 15:1; 1:10 to 10:1; 1:5 to 5:1; 1:2 to 2:1; 1:100 to 1:1; 1:75
to 1:1; 1:50 to 1:1; 1:25 to 1:1; 1:15 to 1:1; 1:10 to 1:1; 1:5 to
1:1; 1:2 to 1:1; 1:10 to 2:1.
[0078] When the catalyst compounds are ligated metal dihalide
compounds, a co-activator is always used when an NCA activator is
used.
[0079] Other catalysts, including heterogeneous catalyst such as
zeolites, may be used for the oligomerization. However, the
oligomerization process may not be as clean, e.g., producing more
isomers and fewer linear alpha olefins. Zeolites that may be
suitable for this conversion include, but are not limited to
10-ring zeolites such as ZSM-5 (MFI), ZSM-11 (MEL), ZSM-48 (MRE),
and the like, with Si/Al.sub.2 ratios from 5 to 500. The zeolites
are used in their proton form and may or may not be promoted with
metals by ion exchange or impregnation. In addition, the binder
used during formulation may have an effect on the yield and product
slate.
[0080] The oligomerization process can be performed as a single
step process or a two-step process. In a single step process, all
of the oligomerization is performed in a single stage or in a
single reactor in the oligomerization reactor 112. The
oligomerization feed stream 110 is introduced into the single stage
generally as a gas phase feed. The oligomerization feed stream 110
is contacted with the homogeneous catalyst 114 under effective
oligomerization conditions. A solvent, such as hexane, may be used
for the oligomerization process, and recycled. The ethylene feed
may be contacted with the homogenous catalyst 114 at a temperature
of 20.degree. C. to 300.degree. C. In some examples, the reaction
temperature is at least 25.degree. C., or at least 50.degree. C.,
or at least 100.degree. C., and is 250.degree. C. or less, or
225.degree. C. or less. The total pressure can be from 1 atm (100
kPa) to 200 atm (20.2 MPa). In some examples, the total pressure is
100 atm (10.1 MPa) or less. In some examples, the oligomerization
feed is contacted with the catalyst at a hydrogen partial pressure
that is at least 1% of the total pressure, such as at least 5% of
the total pressure or at least 10% of the total pressure or up to
about 50% on a volumetric basis. The reaction forms a raw oligomer
stream 116 that can then be fractionated in a distillation column
118. An optional step of to quench the catalyst may be used, which
consists of using a base, either aqueous or organic, before the
fractionation.
[0081] In the distillation column 118, three streams may be
separated from the raw oligomer stream 116. These may include a
light olefinic stream 120, an intermediate olefinic stream 122 and
a heavy olefinic stream 124. It may be noted that the olefinic
streams 120, 122, and 124 may not be composed of 100% olefinic
compounds, but may include a number of other compounds, such as
paraffins, that are removed in the same boiling point ranges as the
olefinic compounds. As higher molecular weight compounds are
formed, the amounts of paraffinic compounds may increase as
well.
[0082] The light olefinic stream 120 may include, for example,
linear alpha-olefins having from about four carbon atoms to about
10 carbon atoms and unreacted ethylene. Further, as higher
molecular weight compounds are formed, the amounts of paraffinic
compounds may increase as well. The light olefinic stream 120 may
be processed to separate an unreacted ethylene stream 126 which may
be combined with the oligomerization feed stream 110 and provided
to the oligomerization reactor 112. After separation of the
unreacted ethylene stream 126, the remaining stream 128 may be
processed to recover linear alpha-olefins, for example, having less
than about 12 carbon atoms. This separation may be performed by a
distillation column, a cold box, or other separation methods.
[0083] The intermediate olefinic stream 122 may be provided to a
dimerization reactor 130. As an example, the intermediate olefinic
stream 122 may include compounds having about 12 carbon atoms to
compounds having about 22 carbon atoms, although this may be
adjusted based on the takeoff point in the distillation column 118.
In the dimerization reactor 130, the intermediate olefinic stream
122 may be contacted with a homogeneous or heterogeneous catalyst
to be dimerized to form carbon compounds having about 24 carbon
atoms to about 44 carbon atoms. The reaction may be run at a
temperature of about 50.degree. C. to about 400.degree. C., and a
pressure of about 50 psig to about 2000 psig. The dimerized stream
132 may be returned to the distillation column 118, in which lower
carbon number compounds, such as unreacted compounds having about
12 carbon atoms to about 22 carbon atoms, may be further sent to
the dimerization reactor 130 for processing.
[0084] The heavy olefinic stream 124, may have at least about 24
carbon atoms. To lower the amounts of contaminants, as well as to
upgrade the final products, the heavy olefinic stream 124 may be
provided to a hydro-processing reactor 134 to remove contaminants
and improve product properties, such as cold flow properties. For
example, hydrotreatment or mild hydrocracking can be used for
removal of contaminants, and optionally to provide some viscosity
index uplift, while hydrocracking and hydroisomerization, termed
catalytic HDC/HDI, may be used to improve cold flow properties.
Hydro-Processing
[0085] As used herein, "hydro-processing" includes any hydrocarbon
processing that is performed in the presence of hydrogen. The
hydrogen may be added to the hydro-processing reactor 134 as a
hydrogen treat stream 136. The hydrogen treat stream 136 is fed or
injected into a vessel or reaction zone or hydro-processing zone in
which the hydro-processing catalyst is located. The hydrogen treat
stream 136 may be pure hydrogen or a hydrogen-containing gas, which
is a gas stream containing hydrogen in an amount that is sufficient
for the intended reactions. The hydrogen treat stream 136 may
include one or more other gasses, such as nitrogen and light
hydrocarbons, that do not interfere with or affect either the
reactions or the products. Impurities, such as H.sub.2 S and
NH.sub.3 are undesirable and would typically be removed from the
hydrogen treat stream 136 before it is conducted to the reactor.
The hydrogen treat stream 136 introduced into a reaction stage may
include at least 50 vol. % hydrogen or at least 75 vol. % hydrogen.
The products of the hydro-processing reactor 134, termed a
hydro-processed stream 138, may have lower contaminants, including
metals and heteroatom compounds, as well as improved viscosities,
viscosity indices, saturates content, low temperature properties,
volatilities and depolarization, and the like.
[0086] Various types of hydro-processing can be used in the
production of fuels and base oil stocks, such as hydroconversion,
hydrocracking, hydrogenation, hydrotreating, hydrodesulfurization,
hydrodenitrogenation, hydrodemetallation, and hydroisomerization,
among others. Typical processes include a demetallation process to
remove metallic remnants of the catalyst. Further, a catalytic
dewaxing, or hydrocracking/hydroisomerization (HDC/HDI) process,
may be included to modify viscosity properties or cold flow
properties, such as pour point and cloud point. The hydrocracked or
dewaxed feed can then be hydrofinished, for example, to saturate
olefins and aromatics from the heavy olefinic stream 124. In
addition to the above, a hydrotreatment stage can also be used for
contaminant removal. The hydrotreatment of the oligomer feed to
remove contaminants may be performed prior to or after the
hydrocracking or the HDC/HDI.
[0087] In the discussion below, a stage in a hydro-processing
reactor 134 can correspond to a single reactor or a plurality of
reactors. In some examples, multiple reactors can be used to
perform one or more of the processes, or multiple parallel reactors
can be used for all processes in a stage. Each stage or reactor may
include one or more catalyst beds containing hydro-processing
catalyst. Note that a catalyst bed in the discussion below may
refer to a partial physical catalyst bed. For example, a catalyst
bed within a reactor could be filled partially with a hydrocracking
catalyst and partially with an HDC/HDI catalyst. For convenience in
description, even though the two catalysts may be stacked together
in a single catalyst bed, the hydrocracking catalyst and the
HDC/HDI catalyst can each be referred to conceptually as separate
catalyst beds. As an example, the hydro-processing reactor 134
shown in FIG. 1 includes a demetallation reactor 134A and a
hydrocracking/hydroisomerization (HDC/HDI) reactor 134B, shown as
separate reactors or units.
Hydrodemetallation
[0088] The demetallation reactor 134A includes a demetallation
catalyst and operates at about 200-500.degree. C. and 50-1200 psi.
The demetallation reactor removes metals in the homogeneous
catalyst, such as Fe and Al, from the organic components, which are
deposited on the solid catalysts. The demetallation reactor is
typically used for the removal of metals in petroleum oil. The
metals in petroleum oil exists as metal complexes, much like the in
metals in the homogeneous catalysts.
Hydroisomerization/Hydrocracking (HDC/HDI)
[0089] In the HDC/HDI reactor 134B, suitable HDC/HDI (dewaxing)
catalysts may include molecular sieves such as crystalline
aluminosilicates, or zeolites. In various examples, the molecular
sieve includes ZSM-5, ZSM-22, ZSM-23, ZSM-35, ZSM-48, SAPO-11,
zeolite Beta, or zeolite Y, or includes combinations thereof, such
as ZSM-23 and ZSM-48, or ZSM-48 and zeolite Beta. Molecular sieves
that are selective for dewaxing by isomerization, as opposed to
cracking, may be used, such as ZSM-48, ZSM-23, SAPO-11 or any
combinations thereof. The molecular sieves may include a 10-member
ring 1-D molecular sieve. Examples include EU-1, ZSM-35 (or
ferrierite), ZSM-11, ZSM-57, NU-87, SAPO-11, ZSM-48, ZSM-23, and
ZSM-22. Some of these materials may be more efficient, such as
EU-2, EU-11, ZBM-30, ZSM-48, or ZSM-23. Note that a zeolite having
the ZSM-23 structure with a silica to alumina ratio of from 20:1 to
40:1 may be referred to as SSZ-32. Other molecular sieves that are
isostructural with the above materials include Theta-I, NU-10,
EU-13, KZ-1, and NU-23. The HDC/HDI catalyst may include a binder
for the molecular sieve, such as alumina, titania, silica,
silica-alumina, zirconia, or a combination thereof, for example
alumina and titania or silica and zirconia, titania, or both.
[0090] In various examples, the catalysts according to the
disclosure further include a hydrogenation catalyst to saturate
olefins and aromatics, which may be termed hydrofinishing herein.
The hydrogenation catalyst typically includes a metal hydrogenation
component that is a Group VI and/or a Group VIII metal. In some
examples, the metal hydrogenation component is a Group VIII noble
metal. For example, the metal hydrogenation component may be Pt,
Pd, or a mixture thereof. Further, the metal hydrogenation
component may be a combination of a non-noble Group VIII metal with
a Group VI metal. Suitable combinations can include Ni, Co, or Fe
with Mo or W, or, in some examples, Ni with Mo or W.
[0091] The metal hydrogenation component may be added to the
catalyst in any convenient manner. For example, the metal
hydrogenation component may be combined with the catalyst using an
incipient wetness. In this technique, after combining a zeolite and
a binder, the combined zeolite and binder can be extruded into
catalyst particles. These catalyst particles may then be exposed to
a solution containing a suitable metal precursor. In some examples,
metal can be added to the catalyst by ion exchange, where a metal
precursor is added to a mixture of zeolite (or zeolite and binder)
prior to extrusion.
[0092] The amount of metal in the catalyst may be at least about
0.1 wt. % based on catalyst, or at least about 0.15 wt. %, or at
least about 0.2 wt. %, or at least about 0.25 wt. %, or at least
about 0.3 wt. %, or at least about 0.5 wt. % based on catalyst. The
amount of metal in the catalyst may be about 20 wt. % or less based
on catalyst, or about 10 wt. % or less, or about 5 wt. % or less,
or about 2.5 wt. % or less, or about 1 wt. % or less. For examples
where the metal is Pt, Pd, another Group VIII noble metal, or a
combination thereof, the amount of metal may be from about 0.1 to
about 5 wt. %, about 0.1 to about 2 wt. %, or about 0.25 to about
1.8 wt. %, or about 0.4 to about 1.5 wt. %. For examples where the
metal is a combination of a non-noble Group VIII metal with a Group
VI metal, the combined amount of metal may be from about 0.5 wt. %
to about 20 wt. %, or about 1 wt. % to about 15 wt. %, or about 2.5
wt. % to about 10 wt. %.
[0093] The HDC/HDI catalysts may also include a binder. In some
examples, the HDC/HDI catalysts may use a low surface area binder.
A low surface area binder represents a binder with a surface area
of about 100 m.sup.2/g or less, or 80 m.sup.2/g or less, or about
70 m.sup.2/g or less. The amount of zeolite in a catalyst
formulated using a binder can be from about 30 wt. % zeolite to
about 90 wt. % zeolite relative to the combined weight of binder
and zeolite. In some examples, the amount of zeolite may be at
least about 50 wt. % of the combined weight of zeolite and binder,
such as at least about 60 wt. % or from about 65 wt. % to about 80
wt. %.
[0094] A zeolite can be combined with binder in any convenient
manner. For example, a bound catalyst can be produced by starting
with powders of both the zeolite and binder, combining and mulling
the powders with added water to form a mixture, and then extruding
the mixture to produce a bound catalyst of a desired size.
Extrusion aids can also be used to modify the extrusion flow
properties of the zeolite and binder mixture.
[0095] Process conditions in a catalytic HDC/HDI zone in a may
include a temperature of from about 200 to about 450.degree. C., or
from about 270 to about 400.degree. C., a hydrogen partial pressure
of from about 1.8 MPag to about 34.6 MPag (about 250 psig to about
5000 psig), or from about 4.8 MPag to about 20.8 MPag, and a
hydrogen circulation rate of from about 35.6 m.sup.3/m.sup.3 (200
SCF/B) to about 1781 m.sup.3/m.sup.3 (10,000 SCF/B), or from about
178 m.sup.3/m.sup.3 (1000 SCF/B) to about 890.6 m.sup.3/m.sup.3
(5000 SCF/B). In other examples, the conditions can include
temperatures in the range of about 343.degree. C. (600.degree. F.)
to about 435.degree. C. (815.degree. F.), hydrogen partial
pressures of from about 3.5 MPag-20.9 MPag (about 500 psig to 3000
psig), and hydrogen treat gas rates of from about 213
m.sup.3/m.sup.3 to about 1068 m.sup.3/m.sup.3 (1200 SCF/B to 6000
SCF/B). These latter conditions may be suitable, for example, if
the HDC/HDI stage is operating under sour conditions, e.g., in the
presence of high concentrations of sulfur compounds.
[0096] The liquid hourly space velocity (LHSV) can vary depending
on the ratio of hydrocracking catalyst used to hydroisomerization
catalyst in the HDC/HDI catalyst. Relative to the combined amount
of hydrocracking and hydroisomerization catalyst, the LHSV may be
from about 0.2 h.sup.-1 to about 10 h.sup.-1, such as from about
0.5 h.sup.-1 to about 5 h.sup.-1 and/or from about 1 h.sup.-1 to
about 4 h.sup.-1. Depending on the ratio of hydrocracking catalyst
to hydroisomerization catalyst used, the LHSV relative to only the
HDC/HDI catalyst can be from about 0.25 h.sup.-1 to about 50
h.sup.-1, such as from about 0.5 h.sup.-1 to about 20 h.sup.-1, or
from about 1.0 h.sup.-1 to about 4.0 h.sup.-1
Hydrotreatment Conditions
[0097] Hydrotreatment may be used to reduce the sulfur, nitrogen,
and aromatic content of the heavy olefinic stream 124, for example,
removing nitrogen compounds from the oligomerization catalyst. The
catalysts used for hydrotreatment may include hydro-processing
catalysts that include at least one Group VIII non-noble metal
(Columns 8-10 of IUPAC periodic table), such as Fe, Co, or Ni, or
Co or Ni, and at least one Group VI metal (Column 6 of IUPAC
periodic table), such as Mo or W. Such hydro-processing catalysts
may include transition metal sulfides that are impregnated or
dispersed on a refractory support or carrier such as alumina or
silica. The support or carrier itself typically has no significant
or measurable catalytic activity. Substantially carrier- or
support-free catalysts, commonly referred to as bulk catalysts,
generally have higher volumetric activities than their bound
counterparts.
[0098] In addition to alumina or silica, other suitable support or
carrier materials can include, but are not limited to, zeolites,
titania, silica-titania, and titania-alumina. Suitable aluminas
include porous aluminas, such as gamma or eta forms, having average
pore sizes from about 50 to about 200 Angstrom (.ANG.), or about 75
to about 150 .ANG.; a surface area from about 100 to about 300
m.sup.2/g, or about 150 to about 250 m.sup.2/g; and a pore volume
of from about 0.25 to about 1.0 cm.sup.3/g, or about 0.35 to about
0.8 cm.sup.3/g. Generally, any convenient size, shape, or pore size
distribution for a catalyst suitable for hydrotreatment of a
distillate (including lubricant base oil) boiling range feed in a
conventional manner may be used. Further, more than one type of
hydro-processing catalyst can be used in one or multiple reaction
vessels. A Group VIII non-noble metal, in oxide form, may be
present in an amount ranging from about 2 wt. % to about 40 wt. %,
or from about 4 wt. % to about 15 wt. %. A Group VI metal, in oxide
form, can typically be present in an amount ranging from about 2
wt. % to about 70 wt. %, or, for bound catalysts, from about 6 wt.
% to about 40 wt. % or from about 10 wt. % to about 30 wt. %. These
weight percentages are based on the total to weight of the
catalyst. Suitable metal catalysts include cobalt/molybdenum (for
example, including about 1-10% Co as oxide and about 10-40% Mo as
oxide), nickel/molybdenum (including about 1-10% Ni as oxide and
about 10-40% Co as oxide), or nickel/tungsten (including about
1-10% Ni as oxide and about 10-40% W as oxide) on alumina, silica,
silica-alumina, or titania, among others.
[0099] The hydrotreatment is carried out in the presence of
hydrogen, for example, from the hydrogen treat stream 136.
Hydrotreating conditions can include temperatures of about
200.degree. C. to about 450.degree. C., or about 315.degree. C. to
about 425.degree. C.; pressures of about 250 psig (1.8 MPag) to
about 5000 psig (34.6 MPag) or about 300 psig (2.1 MPag) to about
3000 psig (20.8 MPag); liquid hourly space velocities (LHSV) of
about 0.1 hr.sup.-1 to about 10 hr.sup.-1; and hydrogen treat rates
of about 200 SCF/Btu (35.6 m.sup.3/m.sup.3) to 10,000 SCF/Btu (1781
m.sup.3/m.sup.3) or about 500 (89 m.sup.3/m.sup.3) to about 10,000
SCF/B (1781 m.sup.3/m.sup.3) or about 3000 psig (3.5 MPag-20.9
MPag), and hydrogen treat gas rates of from about 213
m.sup.3/m.sup.3 to about 1068 m.sup.3/m.sup.3 (1200 SCF/Btu 6000
SCF/Btu).
Hydrofinishing and Aromatic Saturation Process
[0100] In some examples, a hydrofinishing stage, an aromatic
saturation stage, or both may be used. These stages are termed
finishing processes herein. Finishing processes may improve color
and stability in a final product by lowering the amounts of
unsaturated or oxygenated compounds in the final product streams.
The finishing may be performed in the hydro-processing reactor 134
after the last hydrocracking or hydroisomerization stage. Further,
the finishing may occur after fractionation of a hydro-processed
stream 138 in a product distillation column 140. If finishing
occurs after fractionation, the finishing may be performed on one
or more portions of the fractionated product. In some examples, the
entire effluent from the last hydrocracking or HDC/HDI process can
be finished prior to fractionation into individual product
streams.
[0101] In some examples, the finishing processes, including
hydrofinishing and aromatic saturation, refer to a single process
performed using the same catalyst. Alternatively, one type of
catalyst or catalyst system can be provided to perform aromatic
saturation, while a second catalyst or catalyst system can be used
for hydrofinishing. Typically the finishing processes will be
performed in a separate reactor from the HDC/HDI or hydrocracking
processes to facilitate the use of a lower temperature for the
finishing processes. However, an additional hydrofinishing reactor
following a hydrocracking or HDC/HDI process, but prior to
fractionation, may still be considered part of a second stage of a
reaction system conceptually.
[0102] Finishing catalysts can include catalysts containing Group
VI metals, Group VIII metals, and mixtures thereof. In an example,
the metals may include a metal sulfide compound having a strong
hydrogenation function. The finishing catalysts may include a Group
VIII noble metal, such as Pt, Pd, or a combination thereof. The
mixture of metals may also be present as bulk metal catalysts
wherein the amount of metal is 30 wt. % or greater based on the
catalyst. The metals and metal compounds may be bound, for example,
on a metal oxide. Suitable metal oxide supports include low acidic
oxides such as silica, alumina, silica-aluminas or titania, or, in
some examples, alumina.
[0103] The catalysts for aromatic saturation may include at least
one metal having relatively strong hydrogenation function on a
porous support. Typical binding materials include amorphous or
crystalline oxide materials such as alumina, silica, and
silica-alumina. The binding materials may also be modified, such as
by halogenation or fluorination. The metal content of the catalyst
may be as high as 20 wt. % for non-noble metals. In an example, a
hydrofinishing catalyst may include a crystalline material
belonging to the M41S class or family of catalysts. The M41S family
of catalysts are mesoporous materials having high silica content.
Examples include MCM-41, MCM-48 and MCM-50. Examples include
MCM-41, MCM-48, MCM-49, and MCM-50. Other catalysts that may be
used include Beta, Y, and other large pore zeolites (12-member ring
MR and up). If separate catalysts are used for aromatic saturation
and hydrofinishing, an aromatic saturation catalyst can be selected
based on activity or selectivity for aromatic saturation, while a
hydrofinishing catalyst can be selected based on activity for
improving product specifications, such as product color and
polynuclear aromatic reduction.
[0104] Hydrofinishing conditions can include temperatures from
about 125.degree. C. to about 425.degree. C., or about 180.degree.
C. to about 280.degree. C., a hydrogen partial pressure from about
500 psig (3.4 MPa) to about 3000 psig (20.7 MPa), or about 1500
psig (10.3 MPa) to about 2500 psig (17.2 MPa), and an LHSV from
about 0.1 hr.sup.-1 to about 5 hr.sup.-1 LHSV, or, in some
examples, 0.5 hr.sup.-1 to 1.5 hr.sup.-1. Additionally, a hydrogen
treat gas rate of from about 35.6 m.sup.3/m.sup.3 to about 1781
m.sup.3/m.sup.3 (200 SCF/B to 10,000 SCF/B) can be used.
Fractionation and Products
[0105] After hydro-processing, the hydro-processed oligomers in the
hydro-processed stream 138 can be fractionated in the product
distillation column 140. Any number of fractions may be isolated,
including, for example, a distillate stream 142 that may include
hydrocarbon fluids, such as gasoline, naphtha, diesel, or a
distillate fuel fraction, among others. Fractions that form base
oil stocks for lubricants and other hydrocarbon products, may be
isolated, including, for example, a light neutral stream 144, and a
medium neutral stream 146, in addition to a heavy neutral stream
148.
[0106] A bottoms stream 150 may also be isolated. In some examples,
the bottoms stream 150 is returned to the hydro-processing reactor
134 for further processing.
[0107] The system of FIG. 1(A) is not limited to the use of
dimerization for the upgrading of products. In some examples,
alkylation may be used to upgrade the molecular weights and
branching. As used herein, "alkylation" refers to a process in
which a feed stream containing olefins, such the intermediate
olefinic stream 122, is reacted with another stream containing
hydrocarbons, such as a mixed xylenes or naphthalene stream, among
others, in an alkylation reactor. The process converts at least a
portion of the olefinic compounds to higher molecular compounds. An
alkylation reactor may react the feed streams in the presence of a
catalyst, for example, an acid, such as sulfuric acid or
hydrofluoric acid, or a solid acid, such as a zeolite, for example
zeolite Y, zeolite beta, and zeolite of the MWW family, among
others. The alkylation may be run at a temperature of about
150.degree. C. to about 250.degree. C., and a pressure of about 300
psig to about 1000 psig. The process provides an alkylated stream
that may be processed in the alkylation reactor to remove acid and
other contaminants before being provided to a separation or
distillation column.
[0108] In the distillation column, light or unreacted compounds may
be separated into an unreacted stream and blended with the
intermediate olefinic stream to be fed back into the alkylation
reactor. A heavy product stream may be separated out and provided
to the HDC/HDI reactor 134B.
[0109] FIG. 1(B) is a simplified block diagram of a recovery system
108 for purifying an impure ethylene stream formed from the
dehydration of ethanol, in accordance with examples. Like numbered
items are as described with respect to FIG. 1. The recovery system
108 may be as simple as a condenser 152. In this arrangement, the
raw product stream 106, including ethylene, water from the initial
azeotropic mixture, and water from the dehydration process, is fed
to the condenser 152. A coolant-in stream 154 may include water
from a cooling tower, or lower temperature coolants for enhanced
removal of water, such as propane, ammonia, or other coolants. A
coolant-out stream 156 may return the coolant, warmed by condensing
water, to a coolant system. The condensed water may be removed in a
water stream 158, while the ethylene stream 110 exits through a
different port on the vessel and is provided to downstream
processing units, such as the oligomerization reactor 112. As
described herein, other water removal systems may be used, such as
flash tanks, caustic systems, absorption systems, and the like. In
some examples, the purification system may remove other compounds,
such as sulfur compounds and nitrogen compounds, lowering poison
concentrations before the oligomerization process.
[0110] FIG. 2 is a simplified block diagram of another system 200
for producing base oil stocks from a light hydrocarbon stream, in
accordance with examples. Like numbered items are as described with
respect to FIG. 1(A). In this example, the oligomerization feed
stream 110 may be processed to remove carbon monoxide (CO). This
may be performed in a catalytic reactor 160 with an oxygen or
hydrogen stream 162, involving the use of a fixed bed reactor for
selective CO conversion, as described with respect to the examples.
The conditions for such selective conversion of CO may be between
25400 C, or between 50-250 C, and pressure between 50 and 500 psig.
Optionally an adsorption process such as Pressure Swing Adsorption
(PSA) maybe used. Additionally, an adsorbent filled adsorption bed
may be used for the removal of trace amount of CO. After the
removal of the CO, the oligomerization feed stream 110 may be
provided to the oligomerization reactor 112. Although not shown in
FIG. 2, a dimerization reactor, or an alkylation reactor may be
used to upgrade the oligomers. In some examples, other products may
be produced.
[0111] FIG. 3 is a process flow diagram of a method 300 for
producing base oil stocks from a steam cracking process, in
accordance with examples. The method 300 begins at block 302, with
the cracking of a light hydrocarbon stream to form an impure
olefinic mixture. Naphtha, steam cracking gas oil (SCGO), or tar,
among others, may be separated from the impure olefinic mixture,
for example, in a quench tower. Further, hydrogen sulfide, carbon
dioxide, or both, may be separated from the raw product stream, for
example, using a caustic tower or an amine separator.
[0112] At block 304, an oligomerization feed stream may be
recovered from the impure ethylene mixture. This may be performed
by passing the impure olefinic mixture stream through a condenser,
or other separator, to remove water from the impure olefinic
stream. Other actions may be performed for the purification, for
example, passing the output stream from the condenser through a
carbon monoxide oxidation system to remove carbon monoxide.
[0113] At block 306, the oligomerization feed stream may be
oligomerized to form a raw oligomer stream. As described herein,
this may be performed by contacting the oligomerization feed stream
with a homogeneous catalyst to form the raw oligomer stream,
wherein the raw oligomer stream has a substantial concentration of
linear alpha olefins.
[0114] At block 308, a light olefinic stream is distilled from the
raw oligomer stream, and processed to recover light olefins. As
described herein, the light olefins may include linear
alpha-olefins having about four to twenty carbon atoms. An olefinic
stream may not include 100% olefinic compounds, but may include
other compounds, such as paraffinic compounds, that have a similar
boiling point to the olefinic compounds.
[0115] At block 310, a heavy olefinic stream is distilled from the
intermediate stream. At block 312, the heavy olefinic stream is
hydro-processed to form a hydro-processed stream. In the
hydro-processing, the heavy olefinic stream may be
hydrodemetallated to remove any traces of catalyst remaining from
the oligomerization. The heavy olefinic stream may then be
hydrocracked to form lower molecular weight compounds, for example,
having a broader distribution. The heavy olefinic stream may be
hydroisomerized to form a distribution of different isomers.
Further, the heavy olefinic stream may be finished to decrease
unsaturated and aromatic compounds in the hydro-processed
stream.
[0116] At block 314, the hydro-processed stream is distilled to
form the base oil stock. Distilling the hydro-processed stream may
include separating a distillate stream, a naphtha stream, or both
from the hydro-processed stream. These streams may be used as
product streams and provided to other processes. Further,
distilling the hydro-processed stream may include forming a heavy
neutral oil stock stream, a medium neutral oil stock stream, or a
light neutral oil stock stream, or any combinations thereof.
EXAMPLES
Example 1: Composition of Oligomerization Feed Stream
[0117] An example of the weight and volumetric composition of an
oligomerization feed stream formed in the steam cracking of ethane,
after separation with a primary fractionator, a caustic tower, and
a drier, is shown in Table 1.
TABLE-US-00001 TABLE 1 Oligomerization feed stream composition
after simple separation Volume (%) Hydrogen 44.2 Methane 6.37
Acetylene 1.19 Ethylene 36.4 Ethane 11.4 Propylene 0.48 Carbon
Monoxide 0.03
Example 2: Carbon Monoxide Removal from Impure Olefin Stream
[0118] Although the catalysts described herein may convert impure
ethylene to linear alpha olefins and Group III base oil stock in
the presence of carbon monoxide, the rate may be lower. In an
example, a portion, or all, of the CO in the impure feed stream may
be removed, as described with respect to FIG. 2. For example, the
CO may be removed from the feed stream by adsorption onto a fixed
bed pressure swing adsorption system (PSA) or catalytically, by
selective hydrogenation or oxidation.
[0119] The selective hydrogenation of carbon monoxide was tested
over a Rh/Ag/TiO.sub.2 catalyst at 10 WHSV and 50 psig of 50% H2,
49% C2=, 0.9% C3=, and 0.12% CO. At 100.degree. C., the carbon
monoxide conversion was 24% with less than 1% conversion of
ethylene and propylene to ethane and propane, respectively.
Increasing temperature significantly increased carbon monoxide
conversion, but also showed appreciable ethylene to ethane
conversion and propylene conversion, which was undesired.
[0120] FIG. 4 is a plot 400 showing the selective hydrogenation of
carbon monoxide, in accordance with examples. The selective
oxidation of carbon monoxide was tested over an Au/Al2O3 catalyst
at 10 WHSV and 50 psig of 48% H2, 47% C2=, 0.8% C3=, 0.12% CO, 0.1%
O2, 5% N2, and 3% H2O. FIG. 4 is a plot showing the conversion rate
402 of selective oxidation of carbon monoxide to carbon dioxide, in
accordance with examples. The initial activity as high as 60%
conversion rate 402 of carbon monoxide at 70.degree. C., shown as
temperature 404. The high initial conversion rate 402 corresponds
to a high oxygen usage rate 406. The oxygen usage rate 406 levels
as the conversion rate 402 drops. The conversion rate 402 levels at
a constant activity of about 25% conversion of carbon monoxide with
less than about a 1% conversion rate 408 of ethane. The presence of
water greatly increases the activity for carbon monoxide
oxidation.
Example 3: Impure Olefin Stream to Shultz-Flory Molecular
Distribution for LAO and Base Oil Stock Production
[0121] FIGS. 5(A) to 5(E) are drawings of different homogeneous
catalysts that can be used for oligomerization and dimerization
processes, in accordance with examples. The capability of the
homogeneous catalysts to oligomerize the impure olefinic stream to
higher molecular weight products was determined by testing the
material in a batch reactor. As described herein, the feed stream
may include ethylene, propylene, hydrogen, methane, ethane,
propane, acetylene, and carbon monoxide, among others.
[0122] The tests of the catalysts in the oligomerization process
were performed in a 500 milliliter (mL) autoclave. 100 mL toluene
solution containing 20 micromoles (.mu.mol) catalyst and 4000
.mu.mol MAO activator was charged to the autoclave. Then a
predetermined amount of N.sub.2, a mixture of H.sub.2 and N.sub.2,
or a mixture with other gases, as described with respect to Tables
1-3, was charged into the autoclave to bring the autoclave to a
preset pressure. The autoclave was then heated to 50.degree. C.
before ethylene was introduced. The reaction was exothermic and
ethylene addition was controlled to keep the temperature below
about 120.degree. C. and a final total pressure of about 400 psi.
The oligomerization reaction was allowed to proceed for
approximately 30 minutes.
[0123] The autoclave was then cooled to room temperature and
overhead gas pressure was released via opening of a valve. The
reaction product, in the form of a solution (suspension) was then
recovered. The solution was quenched with an aqueous HCl solution,
and the aqueous phase containing Fe and Al was discarded. The
reaction product was analyzed via gas chromatography (GC) and
nuclear magnetic resonance (NMR) techniques.
[0124] The gas chromatography analysis for ethylene oligomers was
performed using a method that enabled coverage up to C30. The
column was 30 m long, with an inner diameter of 0.32 millimeters
and a packing of 0.25 .mu.m, available as a HP-5 column from
Agilent. The carrier gas was nitrogen. The injector was held at a
temperature of 150.degree. C. and 10 psi. A 50 to 1 split ratio was
used with a 121 mL per minute (mL/min) total flow rate and an
injection size of 1-5 .mu.L. The column oven was set to a
50.degree. C. initial temp with a 10.degree. C./min ramp rate to a
320.degree. C. final temperature. It was held at the 320.degree. C.
temperature for 8 minutes giving a total run time of 35 minutes.
The detector was a flame ionization detector held at 300.degree.
C., using a 30 mL/min flow of hydrogen, a 250 mL/min flow of air,
and a 25 mL/min makeup stream of nitrogen. The gas chromatography
analysis for dimerization or alkylation products was performed
using a high temperature method to enable coverage up to C100. The
column was 6 m long, with an inner diameter of 0.53 millimeters and
a packing of 0.15 .mu.m, available as a MXT-1 SimDist column from
Restek company of State College, Pa. The carrier gas was nitrogen.
The injector was held at a temperature of 300.degree. C. and 0.9
psi. A 15 to 1 split ratio was used with a 27.4 mL per minute
(mL/min) total flow rate and an injection size of 1 .mu.L. The
column oven was set to an 80.degree. C. initial temp with a
15.degree. C./min ramp rate to a 400.degree. C. final temperature.
It was held at the 400.degree. C. temperature for 15 minutes giving
a total run time of 36.3 minutes. The detector was a flame
ionization detector held at 300.degree. C., using a 40 mL/min flow
of hydrogen, a 200 mL/min flow of air, and a 45 mL/min makeup
stream of nitrogen.
[0125] The C-13 NMR analysis was performed using a Bruker 400 MHz
Advance III to spectrophotometer. The samples were dissolved in
chloroform-D (CDCl.sub.3) or toluene-D8 in a 5 mm NMR tube at
concentrations of between 10 to 15 wt. % prior to being inserted
into the spectrophotometer. The C-13 NMR data was collected at room
temperature (20.degree. C.). The spectra were acquired with time
averaging to provide a signal to noise level adequate to measure
the signals of interest. Prior to data analysis, spectra were
referenced by setting the chemical shift of the CDCl.sub.3 solvent
signal to 77.0 ppm.
[0126] H-1 NMR data was collected at room temperature. The data was
recorded using a maximum pulse width of 45 degree, 8 seconds
between pulses and signal averaging of 120 transients.
[0127] The analyses confirmed that the products were mostly linear
alpha-olefins (LAOS) having Schulz-Flory (S-F) distributions. The
S-F distribution constant, a, was determined by an average of the
molar ratios of C16/C14; C14/C12; and C12/C10 in the product, as
determined by gas chromatography.
[0128] The information in Table 2 shows the basic comparison
between oligomerizations performed using catalysts A-D. For these
runs, the reaction conditions included about 200 psi of ethylene,
about 200 psi of hydrogen, a reaction temperature of about
80.degree. C. to 100.degree. C., 100 mL of toluene (as a catalyst
solvent), 20 .mu.mol of catalyst, and a ratio of 200 mol/mol of
activator (co-catalyst) to catalyst, such as the MAO activators
described herein.
TABLE-US-00002 TABLE 2 Comparison of oligomerization by catalyst
A-D % Linear Alpha Alpha % Branched % Linear Example Catalyst Value
Olefin* Olefins* Paraffin* X1 A 0.339 66.6 22.1 1.6 X2 B 0.667 92.9
5.2 1.2 X3 C 0.828 96.0 1.1 2.4 X4 D 0.947 34.5 0.2 64.7 *Presented
in C12 fraction as determined by gas chromatography and mass
spectrometry
[0129] These results indicate that the paraffin/olefin ratio and
S-F distribution may be changed by designing the ligand of the
Fe-complex. Further, the oligomerization is tolerant of large
amount of H.sub.2 and a variety of solvents.
[0130] FIG. 6 is a plot 600 of the Schultz-Flory distribution of a
product that includes different carbon numbers, in accordance with
examples. The weight fraction of the Schulz-Flory product
distribution with experimentally obtained a values may be plotted
against the carbon number in the product. The same data can be
recast to show lumped fraction distribution as a function of a
value.
[0131] FIG. 7 is a plot 700 of the effect of the change in carbon
number composition on a weight fraction of a product as the
Schultz-Flory distribution changes, in accordance with examples.
The plot 700 shows C24-, C24-050, and C52+ fractions as a function
of a value, indicating that the lube molecule range C24-050 has a
maximum value of about 40 wt. % at an a value around 0.88. This
further illustrates that the lube/LAO split may be effectively
controlled by using different catalysts that offer different a
values.
Example 4: Effect of Hydrogen Impurity on an Oligomerization Using
an Fe-PBI Catalyst
[0132] Catalyst B, shown in FIG. 5(B), was chosen to determine the
effects of changing the ratio of hydrogen to nitrogen on the
reaction. The procedure was as described with respect to Example 3.
The results are shown in Table 3. For these runs, the reaction
conditions included about 200 psi of ethylene, about 200 psi of
hydrogen or a mixture of hydrogen and nitrogen, a reaction
temperature of about 80.degree. C. to 100.degree. C., 100 mL of
toluene, 20 .mu.mol of catalyst, and a ratio of 200 mol/mol of
activator (co-catalyst) to catalyst. Examples X2, X5, and X6 show
that the catalyst has a similar product distribution with only a
small paraffin concentration (mostly LAO) across an order of
magnitude change in hydrogen concentration. Thus, the hydrogen
impurity does not greatly affect the product distribution across an
Fe-PBI catalyst.
TABLE-US-00003 TABLE 3 Comparison of oligomerization under changing
ratios of hydrogen and nitrogen using catalyst B Alpha Value %
Linear Example Catalyst H2, psi (.alpha.) Paraffin* X2 B 200 0.667
1.2 X5 B 20 0.664 0.7 X6 B 1.5 0.698 1.1 *Presented in C12 fraction
as determined by gas chromatography and mass spectrometry
Example 5: Effect of CO Impurity on an Oligomerization Using an
Fe-PBI Catalyst
[0133] Catalyst E, shown in FIG. 5(E) was tested using the
procedure in Example 3 with and without carbon monoxide poison in
the feed at constant ethylene partial pressure, with the results
shown in Table 4. The run used 24.6 .mu.mol of catalyst with a 500
to 1, mol to mol ratio of MAO to catalyst. The gas mixture that was
blended with hydrogen and ethylene contained 82.7% C2=, 10.6% C2,
6.1% CH4, 0.5% C3=, and 0.1% CO. When blended 50/50 with hydrogen,
the final concentration of CO was 0.05%. The rate was determined by
the moles of ethylene converted to product per moles of catalyst.
The relative rate is determined compared to the rate with just
ethylene/hydrogen in the feed. The rate decreases by an order of
magnitude when carbon monoxide in the feed.
[0134] However, for catalyst E, carbon monoxide does not completely
terminate the oligomerization reaction despite the decrease in
rate. In contrast, other iron catalysts tested were not active when
CO was present.
TABLE-US-00004 TABLE 4 Effects of CO on oligomerization C2 = Mix H2
CO Relative Example (psig) (psig) (psig) (ppm) Rate X7 100 0 100 0
100% X8 50 50 100 500 7.1%
Example 6: Effects of Carbon Monoxide and Acetylene Impurities on
Oligomerization
[0135] Catalyst E was tested using the procedure in Example 3 with
both carbon monoxide and acetylene poison in the feed at constant
ethylene partial pressure. The run contained 24.6 .mu.mol of
catalyst with a 500 to 1, mol to mol ratio of MAO to catalyst. The
gas mixture that was eventually blended with hydrogen and ethylene
contained 81.7% C2=, 10.5% C2, 6.0% CH4, 1.2% Acetylene, 0.5% C3=,
and 0.1% CO. The relative rate of the CO and acetylene containing
mixture to that of the mixture just containing CO is 90.3%. Thus,
acetylene not only does not inhibit the activity of the catalyst,
but also incorporates into the product as observed by FT-IR
microspectroscopy.
[0136] FIG. 8 is a plot 800 of an IR spectrum showing the
incorporation of acetylene into the product, in accordance with
examples. The incorporation of acetylene into the product was
confirmed by peaks corresponding to trans-polyacetylene at 3015
wavenumbers 802 and 1010 wavenumbers 804.
[0137] FIG. 9 is an infrared micrograph 900, showing the presence
of polyacetylene in a product, in accordance with examples. In the
micrograph, regions of KBr 902, polyethylene 904, and
poly(acetylene) 906 are visible.
Example 7: Effect of Ligands on Co-Production of Group III+ Base
Oil Stock and LAO with Impure Ethylene
[0138] The oligomerization of 50/50 ethylene/hydrogen with various
Fe-PBI catalysts was shown to provide a product slate that was
adjustable by catalyst ligand modification at 400 psig total
pressure and 80 C. The ability to tune MW selectivity with the
catalyst allows the preferred amount of LAO and Group III+ base oil
stock, such as the yield of C24-C50 compounds, to be produced that
maximizes flexibility and profitability. FIG. 10 is a plot 1000
comparing ligand structure to the yield of higher carbon number
compounds, in accordance with examples. The individual data points
are labeled with A to F corresponding to the catalyst from FIGS.
5(A) to 5(F).
[0139] FIGS. 11(A) to 11(C) are comparisons of three plots showing
the ability to tune the molecular weight distribution of the
products using ligand modification, in accordance with examples.
Each of the figures are labelled with the corresponding catalysts,
from FIGS. 5(A), 5(C), and 5(D), used to produce the sample.
Embodiments
[0140] The embodiments of the present techniques include any
combinations of the examples in the following numbered
paragraphs.
[0141] 1. A system for manufacturing a base oil stock from a light
hydrocarbon stream, including a cracker configured to form a raw
hydrocarbon stream from the light hydrocarbon stream, a separator
configured to separate a raw olefinic stream from the raw
hydrocarbon stream, and an oligomerization reactor configured to
increase a number of carbon atoms in molecules of the raw olefinic
stream forming a raw oligomer stream. The system also includes a
distillation column configured to separate the raw oligomer stream
into a light olefinic stream, an intermediate olefinic stream, and
a heavy olefinic stream, wherein the light olefinic stream is
provided to another separator for the isolation of light linear
alpha-olefins. A hydro-processing reactor is configured to
hydro-process the heavy olefinic stream to form a hydro-processed
stream, and a product distillation column is configured to separate
the hydro-processed stream to form the base oil stock.
[0142] 2. The system of Embodiment 1, including a dimerization
reactor configured to dimerize the intermediate olefinic stream and
return a dimerized stream to the distillation column.
[0143] 3. The system of either of Embodiments 1 or 2, including an
alkylation reactor configured to alkylate the intermediate olefinic
stream and provide a raw alkylated stream to an alkylation
distillation column.
[0144] 4. The system of any of Embodiments 1 to 3, wherein the
alkylation distillation column is configured to separate an
unreacted olefin stream from the raw alkylated stream and return
the unreacted olefin stream to the alkylation reactor.
[0145] 5. The system of any of Embodiments 1 to 4, wherein the
alkylation distillation column is configured to separate an
alkylated stream from the raw alkylated stream and provide the
alkylated stream to the hydro-processing reactor.
[0146] 6. The system of any of Embodiments 1 to 5, wherein the
separator includes a primary fractionator configured to remove tar
and steam cracker gas oil from the raw hydrocarbon stream, a
caustic tower configured to remove hydrogen sulfide and carbon
dioxide from the raw hydrocarbon stream, and a dryer configured to
remove water from the raw hydrocarbon stream.
[0147] 7. The system of any of Embodiments 1 to 6, wherein the
oligomerization reactor is configured to use a homogeneous
catalyst.
[0148] 8. The system of Embodiment 7, wherein the homogeneous
catalyst includes an iron (II) pyridine-bis-imine (Fe-PBI) catalyst
including a structure of,
##STR00004##
wherein Rn includes one, two, or three substituents, and wherein
the substituents include CH.sub.3, F, or both.
[0149] 9. The system of any of Embodiments 1 to 8, wherein the
hydro-processing reactor includes a demetallation unit.
[0150] 10. The system of any of Embodiments 1 to 9, wherein the
hydro-processing reactor includes a hydrocracking unit.
[0151] 11. The system of any of Embodiments 1 to 10, wherein the
hydro-processing reactor includes a hydroisomerization unit.
[0152] 12. The system of any of Embodiments 1 to 11, wherein the
distillation column is configured to separate the hydro-processed
stream into a distillate stream including naphtha, a heavy neutral
stream, a medium neutral stream, and a light neutral stream.
[0153] 13. A method for manufacturing a base oil stock from a light
hydrocarbon stream, including cracking the light hydrocarbon stream
to form an impure olefinic stream, separating water from the impure
olefinic stream, and oligomerizing the impure olefinic stream to
form a raw oligomer stream. The method also includes distilling a
light olefinic stream from the raw oligomer stream and recovering
alpha olefins from the light olefinic stream. A heavy olefinic
stream is distilled from the raw oligomer stream, and the heavy
olefinic stream is hydro-processed to form a hydro-processed
stream. The hydro-processed stream is distilled to form the base
oil stock.
[0154] 14. The method of Embodiment 13, including distilling an
intermediate olefinic stream from the raw oligomer stream.
[0155] 15. The method of either of Embodiments 13 or 14, including
dimerizing the intermediate olefinic stream to form a dimerized
stream, and distilling the dimerized stream with the raw oligomer
stream.
[0156] 16. The method of any of Embodiments 13 to 15, including
alkylating the intermediate olefinic stream to form an alkylated
stream, distilling the alkylated stream to form a lights stream and
a heavies stream, combining the lights stream with the intermediate
olefinic stream to form a combined stream, and alkylating the
combined stream.
[0157] 17. The method of Embodiment 16, including hydro-processing
the heavies stream.
[0158] 18. The method of any of Embodiments 13 to 17, wherein
oligomerizing the impure olefinic stream includes contacting the
impure olefinic stream with a homogeneous catalyst including an
iron (II) pyridine-bis-imine.
[0159] 19. The method of any of Embodiments 13 to 18, including
separating an unreacted ethylene stream from the raw oligomer
stream, and oligomerizing the unreacted ethylene stream with the
impure olefinic stream.
[0160] 20. The method of any of Embodiments 13 to 19, wherein
hydro-processing the heavy olefinic stream includes hydrocracking
the heavy olefinic stream.
[0161] 21. The method any of Embodiments 13 to 20, wherein
hydro-processing the heavy olefinic stream includes
hydroisomerizing the heavy olefinic stream.
[0162] 22. The method of any of Embodiments 13 to 21, wherein
distilling the hydro-processed stream includes separating a
distillate stream, a naphtha stream, or both from the
hydro-processed stream.
[0163] 23. The method of any Embodiments 13 to 22, wherein
distilling the hydro-processed stream includes forming a heavy
neutral oil stock stream, a medium neutral oil stock stream, or a
light neutral oil stock stream, or any combinations thereof.
[0164] 24. A system for manufacturing a base oil stock from a light
hydrocarbon stream, including a steam cracker to form an impure
olefinic stream from the light hydrocarbon stream, a separator
configured to remove naphtha, water, steam cracker gas oil (SCGO),
and tar from the impure olefinic stream, and an oligomerization
reactor configured to convert the impure olefinic stream to a
higher molecular weight stream by contacting the impure olefinic
stream with a homogeneous catalyst. The system also includes a
distillation column configured to recover a light olefinic stream,
wherein the distillation column is configured to separate an
intermediate olefinic stream from the higher molecular weight
stream and send the intermediate olefinic stream to a dimerization
reactor or an alkylation reactor. The distillation column is
configured to separate a heavy olefinic stream from the higher
molecular weight stream. A hydro-processing reactor is configured
to demetallate the heavy olefinic stream, to crack the heavy
olefinic stream, to form isomers in the heavy olefinic stream, or
to hydrogenate olefinic bonds in the heavy olefinic stream, or any
combinations thereof. A product distillation column is included to
separate the isomers in the heavy olefinic stream to form a number
of base oil stock streams.
[0165] 25. The system of Embodiment 24, wherein the dimerization
reactor is configured to dimerize the intermediate olefinic stream
to form a dimerized stream and return the dimerized stream to the
distillation column.
[0166] 26. The system of either of Embodiments 24 or 25, wherein
the alkylation reactor is configured to alkylate the intermediate
olefinic stream to form an alkylated stream.
[0167] 27. The system of any of Embodiments 24 to 26, including an
alkylation distillation column configured to separate the alkylated
stream into a reacted stream and an unreacted stream, and return
the unreacted stream to the alkylation reactor.
[0168] 28. The system of any of Embodiments 24 to 27, wherein the
homogeneous catalyst includes an iron (II) pyridine-bis-imine
(Fe-PBI) compound including a structure of
##STR00005##
wherein Rn includes one, two, or three substituents, and wherein
the substituents include CH.sub.3, F, or both.
[0169] While the present techniques may be susceptible to various
modifications and alternative forms, the embodiments discussed
above have been shown only by way of example. However, it should
again be understood that the techniques is not intended to be
limited to the particular examples disclosed herein. Indeed, the
present techniques include all alternatives, modifications, and
equivalents falling within the true spirit and scope of the
appended claims.
* * * * *